Nightingale
by Darklighter2016
Summary: Set somewhere after 4x9, "Kill Shot", but before the events leading up to 4x23, "Always", so spoiler alert of sorts. "I wish that I had someone who could be there for me and I could be there for him and we could do it together." Beckett realizes that Castle could be that someone. He could be her sanity; he could bring her peace. Based off of Demi Lovato's song Nightingale.


Nightingale

**AN 1: For any of my followers, I know this isn't a Alex/Mitchie story. I completely love Castle, and with the season five finale, really wanted to write a kind of sweet oneshot for Castle and Beckett set in season four. Maybe you'll give it a chance, if Castle is your thing too. Anyways, I hope that someone somewhere likes it in any case. It's based on a song off of Demi Lovato's latest album: Demi. I could be in love with this song, so I just had to write a oneshot for it. I don't own it, nor do I own Castle or any of the characters mentioned in this story.**

* * *

_I can't sleep tonight, wide awake and so confused_

_Everything's in line, but I am bruised_

_I need a voice to echo, I need a light to take me home_

_I kinda need a hero, is it you?_

_I never see the forest for the trees, I could really use your melody_

_Baby I'm a little blind, I think it's time for you to find me_

* * *

Kate Beckett stood beside her living room window, staring out past the clear glass and into the rain-splattered street below. _All these years of solving the worst murders possible, _she thought as she continued to stare outside, _and I still don't understand how some people can do those types of things to another human being. I don't understand how they could do that to _her, _or anyone else, for that matter_. She exhaled softly and ran her hand through her hair before turning away from the window. Her phone buzzed in her pocket, and she pulled the device out wearily. "Beckett," she answered, fighting to keep the exhaustion out of her voice as she did so.

Javier Esposito's voice filtered in through the phone. "The captain gave us the rest of the night off," he said by way of greeting. "Ryan and I were going to head to the Old Haunt for a drink. Lanie said she was going to meet us there. Care to join us?"

Kate attempted a smile, despite the fact that her friend could not see her. "No, thanks, Javi. I think I just want to spend the night in."

Esposito's voice softened in understanding. He recognized that tone. Something was bothering her, but he knew better than to pry. If Beckett wanted to talk, she would come to one of them. If not, it was probably best to simply let her be for the moment, and remind her that she could talk if she wanted or needed to. "Look, Beckett, we're your friends. We're here for you. You know that, right?"

"I know," she replied, moving into her kitchen as she did so. "It's just…today was my mom's birthday. She would have been sixty this year, you know. That's why I didn't come in today. I was with my dad." She fished a glass and a bottle of scotch out of her cabinet and began to pour herself a drink.

"You know where to find us," Esposito replied softly, his voice full of compassion and understanding. "I'm gonna let you go, Beckett, but hit me up if you change your mind and want to be around people tonight."

"I will," Kate murmured, before hitting the end call button and tossing her phone unceremoniously onto the counter beside her. She knocked her drink back neatly and poured herself another one. A glance at the digital clock across from her revealed to her that it was just after ten at night, and she sighed again. _I'm in for a long night,_ she thought, and brought the glass clutched in her hand up to her lips once more.

As she drank, her thoughts turned to a certain dark-haired writer. Richard Castle was quite possibly the most maddening, frustrating, immature, and most ridiculous man she had ever had to deal with in her life. And yet, she couldn't help but smile at the thought of him. The words of her old captain, Roy Montgomery, floated through her mind. "I could've kicked Castle to the curb years ago, any time I wanted to," he had revealed to her. "The only reason I kept him around this long was 'cause I saw how good he was for you. Kate, you're the best that I've ever trained, maybe the best I've ever seen. But you weren't having any fun before he came along." She smiled softly. Montgomery had been right; she hadn't been having fun before Castle. She had been a jaded, wounded mess before he had entered her life and turned everything upside down. She thought back to the first case they had worked together as she took another sip of her drink.

_An extremely angry Detective Kate Beckett burst through the doors of the library. "Richard Castle," she called out loudly, striding towards him. "You are under arrest for felony, theft, and obstruction of justice!" she said after coming to face him._

_He smirked at her, causing her to tighten her jaw in anger. "You forgot making you look bad," he stated cheekily. _

"_You know, for a minute there you actually made me believe that you were human." She turned to the uniformed cops that she had brought with her. "Cuff him."_

"_Ooh, bondage," he grinned as he stood. "My safe word is 'apples'."_

_Fighting the urge to roll her eyes at his cavalier attitude, she addressed the cops again. "Oh, there's no need to be gentle," she stated sharply._

_Castle leaned in as the cops tightened the cuffs around his wrists. "How did you find me, anyways?"_

_Kate arched her eyebrow at him. "I'm a detective," she said smugly. "That's what I do."_

"_My mother told you, didn't she?" he asked._

Kate laughed quietly at the memory and sat her once again empty glass down on the counter next to her phone. He was always something different; a bright spot in the darkness that seemed to consume her life with every case she took. And over the years he had evolved from the guy she couldn't stand to the guy she knew would have her back no matter what circumstances. She could trust him unconditionally, which was something that she had never experienced before him. Running her hand through her hair again, she smiled fondly as another memory, one that was much more recent, rose in her mind.

_Kate walked up to her desk, smiling softly as she noticed Castle sitting in the chair he kept beside her desk. "Hey," she said softly, taking her own seat._

"_Hey," he replied, looking at her as she sat down._

"_What are you doing," she asked him._

"_Just waiting for my partner," he said, causing her to give him a slightly confused look. "Maybe you've seen her. Pretty girl, thinks she can leap tall buildings in a single bound, carries the weight of the world on her shoulders, yet, still manages to laugh at some of my jokes."_

_She smiled, feeling somewhat guilty about how she had been acting towards him for the duration of this case. "She sounds like a handful."_

"_Tell me about it," he replied. "Anyways," he said, standing as he did so, "if you do see her, tell her she owes me about a hundred coffees." He began to walk towards the elevator._

"_Castle?" she called, causing him to stop and look back at her. "Thank you."_

"_For what?" he asked, pretending not to know what she was talking about._

"_For not pushing, and giving me the space to get through this."_

_He smiled at her, gently telling her he understood. "Always."_

Kate smiled again at the memory and tucked a strand of hair behind her ear. Castle had worked her way into her heart and slowly started to destroy the walls that she had been building around herself since her mother's murder. And she found herself not minding this fact nearly as much as she would have once thought. He had become her sanity, her anchor in the storm she seemed to lose herself in. Maybe that was exactly what she needed all this time. She set her empty glass down in the sink and picked up her phone. Kate glanced at the digital clock once more. _12:59, _she noted. _Maybe he's still up._

* * *

A ringing phone jolted Richard Castle from his fitful nap in front of his computer. Blinking blearily, he glanced at the clock in the corner of his screen before answering the phone. "Ah, Detective Beckett," he said around a yawn. "What has you calling me at one in the morning?"

"I'm sorry," her angelic voice came through his phone. "I didn't realize that you were asleep. I, umm, I should go."

"No, no," he responded, sitting up in his chair. "Beckett, I'm your partner. If you need me, I'll be there for you as soon as I can."

He heard her sigh softly. "I couldn't sleep," she admitted, and he smiled to himself at her embarrassed tone. "And I was wondering if maybe you'd…umm…like to come over. We could talk. But, if you're already asleep then obviously you don't have to, I can just go."

He launched himself out of his chair and headed to the front hall closet. "I'll be there as soon as possible," he stated, one hand already through his dark leather jacket.

One short cab ride later, Rick Castle found himself staring at the door of Kate Beckett's apartment. If he was being honest with himself, he was a little nervous. Beckett never called him in the middle of the night just to talk. She was his badass, tough-as-nails partner; she never wanted to admit to needing someone or something else. _Come on, Rick,_ he thought to himself. _She's your partner, and she isn't going to bite you. Just knock on the door and be there for her like you said you would._ He knocked on the door twice and took a small step back.

"Hey, Castle," Kate said with a smile as she opened the door. "Come on in."

"Hey," he replied, smoothing his hands over his jeans before stepping inside the warm apartment. He turned to face her once he was inside. "So, you okay?"

"Yeah, I just…had a kind of rough day," she murmured, running her left hand over her face tiredly and leading him into her living room as she did so.

"We missed you at the precinct today."

Kate smiled softly, causing his heart to melt. "It was my mom's birthday today," she admitted after collapsing onto her couch and gesturing for him to sit with her. "I was with my dad. It's been so long since that day, but I know he still misses her. I do too."

Rick's gaze softened at her confession. "I know," he replied softly, taking the proffered seat next to the weary detective. "It's good that you were there for him though."

"Yeah," she said. "Castle?"

"Hmm?"

She leaned into his shoulder, causing him to start in surprise before wrapping his arm around her. "Do you remember what I said when we thought we had been exposed to the radiation from that bomb scare?"

He laughed softly. "How could I forget? You said 'I wish I could have someone who could be there for me and I could be there for him and we could do it together.' I remember. That case is not something I'll be forgetting anytime soon."

She shifted, arranging her body so that she was leaning with her back to his chest, startling him even more than he was already. "Ever since my mom died, there's been this wall up. You know? And I told you, I don't think I can be the person I want to be until that wall comes down. I don't think I can have the relationship I want until it does. But, something is changing."

"What's that?" Rick asked quietly. He couldn't help but wonder where exactly this conversation was headed. Beckett was never one to simply discuss her feelings, simply out of the blue. Maybe tonight was when that wall would finally come crashing down, as he had been hoping for so long now.

Her voice broke him out of his thoughts. "I realized something tonight, Castle. You've always been there. You're a selfish, immature jackass sometimes, but you've always been there, and you could have quit a long time ago. You've done enough research to make a hundred books, and somehow you just keep showing up to look at some of the worst that humanity seems to offer. You're like…the ray of sunshine in all of the madness we see every day. And, call me crazy, but I think you're the one who's been keeping me sane. You're like a song in the darkness, like my own personal nightingale, leading me home and bringing me peace."

Rick stared in awe at the woman by his side. He had never heard her put so much of herself, of her feelings, on the line before. At his stare, she ducked her head in embarrassment and pulled away abruptly. "Hey," he stuttered, finally finding his voice again and feeling somewhat foolish for his reaction. "Where are you going?"

Kate smiled softly and brushed her hair out of her eyes. "What am I supposed to do, Castle? I just poured my heart out to you, and you sat there and stared at me. I don't know, I thought maybe you felt the same way, but I guess not, so -"

"Whoa, whoa, whoa," he exclaimed, moving closer to her once more. "You have to understand, Kate, I've been wanting you to say that – well, not exactly that because anything I could come up with in my wildest dreams wouldn't compare to that – for a while now. It's a lot to take in, because I never thought you would actually say anything like that to me." Rick took her slender, cool hand in his larger, warmer one gently. "But, if you let me, I will be your nightingale for as long as you want or need. You're right; I've done way more research than I really needed to. Probably more than I'll ever use, in fact. But somewhere along the line it stopped being about the books. It hasn't been purely about the books for quite some time now."

Rick's words caused Kate to smile softly, and she allowed herself to be pulled into his warm embrace without a fight. Slowly, allowing her the time to back away if she wished, he leaned down and placed a gentle kiss on her lips. "I'd like that," she admitted softly, once the kiss had ended. "Castle?"

"Hmm?"

"Say you'll be my nightingale one more time," she asked quietly.

He chuckled softly and rested his forehead against hers softly. "I'll be your nightingale," he murmured gently, and kissed her softly once more. He pulled away, allowing her to settle into him again, her back against his chest, and placed a loving kiss on the top of her head. "So, are you good now?"

Kate looked at their still intertwined hands and grinned. "I'm good," she said. She still carried the pain of her mother's death, and that was unlikely to ever fully go away, but she knew now that she had someone to lean on. Selfish, immature jackass he might be, but he was her selfish, immature jackass. He was her nightingale.

* * *

_Can you be my Nightingale, feel so close I know you're there_

_Ohhhh Nightingale, sing to me, I know you're there._

_Cause baby you're my sanity, you bring me peace, sing me to sleep_

_Say you'll be my Nightingale_

* * *

**AN 2: Well, that's it. Again, I hope that someone liked it. If you did, drop me a review pretty please. I'm starting to work on more stories for other series and pairings rather than just sticking to one, so I guess be on the lookout for those if you're interested. Thanks.  
**


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